This program is directed at the analysis of peptide hormone receptors in testis and ovary, with particular reference to the control of receptor concentration by changes in homologous and heterologous hormones. Desensitization of gonadal adenylate cyclase and steroidogenic responses by gonadotropic hormones is followed by receptor loss and turnover or processing of the hormone-receptor complex. These processes are investigated in Leydig cells and ovarian luteal cells to determine the effects of hormone-induced receptor regulation on gonadal responsiveness, and to analyze the mechanism and consequences of target-cell desensitization. The receptors and direct actions of gonadotropin-releasing hormone (GnRH) in the ovary and testis are also analyzed, in relation to the recently discovered anti-gonadal effects of GnRH agonists.